Why is my Lawnmower Blenny losing weight?

A sunken belly usually indicates starvation. If your tank lacks sufficient natural algae, you must supplement their diet with dried nori, spirulina flakes, or specialised herbivore pellets to keep them healthy.

Will a Lawnmower Blenny eat hair algae?

Yes, they are famous for enthusiastically consuming green hair algae (GHA) and film algae. However, they may ignore certain tough, wiry strains of algae like Bryopsis.

Can I keep two Lawnmower Blennies together?

It is highly discouraged unless you have a confirmed mated pair or an extremely large aquarium (over 500 litres). They are highly territorial towards their own kind and will often fight to the death in standard-sized tanks.

Is the Lawnmower Blenny reef safe?

Generally, yes. They are considered completely reef safe as they ignore corals. However, if they are starving, there are isolated reports of them nipping at fleshy LPS corals or clam mantles out of hunger.

Why is my blenny sitting on my coral?

Perching is a natural behaviour for blennies, as they lack a swim bladder and rest on their pelvic fins. They often choose high vantage points, including large corals, to survey their territory.

MarineMarineBeginner

Lawnmower Blenny

Salarias fasciatus

A highly popular, charismatic marine fish renowned for its insatiable appetite for nuisance algae and comical perching behaviour.

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Ideal Conditions

Temperature: 23 – 28 °C
pH range: 8.1 – 8.4
Hardness: 8 – 12 dGH
Salinity: 1.02 – 1.025 SG
Adult size: 10 – 14 cm
Standard 30-gallon tank: 110 litres+
Lifespan: 2 – 5 years
Diet: Herbivore
Water flow: Moderate
Preferred setup: Ample live rock for grazing and perching; a tight-fitting lid is essential to prevent jumping.

About the Lawnmower Blenny

The Lawnmower Blenny, often referred to as the Algae Blenny, is a staple in the marine aquarium hobby. Characterised by its mottled appearance and expressive face, this benthic species spends its days hopping from rock to rock. They are prized not only for their quirky personalities but also for their utility as excellent natural grazers for reef tanks.

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Is it right for your tank?

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Where Lawnmower Blenny comes from

Native range

Indo-Pacific, Red Sea

Countries / regions

Australia, Indonesia, Philippines, Japan

Habitat

Shallow reef flats, estuarine rubble zones, and rocky shores with abundant microalgae growth.

Widely distributed across the tropical Indo-Pacific basin.

Similar species

Starry Blenny
Salarias ramosus
Tailspot Blenny
Ecsenius stigmatura
Bicolor Blenny
Ecsenius bicolor

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

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Ocellaris Clownfish
Amphiprion ocellaris
Occupy different levels of the aquarium and have no competing dietary or territorial needs.
Great
Yellow Tang
Zebrasoma flavescens
Although both graze on algae, the tang is a free-swimmer and poses no territorial threat to the benthic blenny.
Great
Starry Blenny
Salarias ramosus
Highly territorial towards conspecifics and congenerics; they will viciously fight for grazing territory.
Not recommended
Maxima Clam
Tridacna maxima
Generally safe, but starving blennies have been known to occasionally nip at clam mantles out of desperation.
Compatible with caution
Volitan Lionfish
Pterois volitans
The small, bottom-dwelling blenny will easily become an expensive meal for the predatory lionfish.
Not recommended

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